<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
    }
    
    .father {
        width: 400px;
        height: 400px;
        background-color: coral;
        margin-top: 50px;
        border: 5px solid red;
    }
    
    .father .son {
        width: 200px;
        height: 200px;
        background-color: cornflowerblue;
        margin-top: 100px;
    }
    
    span {
        background-color: darkcyan;
        margin: 20px;
    }
</style>

<body>
    <div class="father">
        <div class="son">
            <span>hahha</span>
        </div>
    </div>
</body>

</html>